TW201435924A - Nanostructure transparent conductors having high thermal stability for ESD protection - Google Patents

Abstract

Disclosed herein are transparent conductors having high thermal capacity and improved protection against electrostatic discharge.

Description

Protecting nanostructured transparent conductors with high thermal stability by electrostatic discharge (ESD)

The present invention relates to a transparent conductor based on a nanostructure in which electrostatic discharge protection is improved.

A transparent conductive system refers to a thin conductive film coated on a high transmittance surface or substrate. Transparent conductors can be fabricated to have surface conductivity while maintaining reasonable optical transparency. Such surface conductive transparent conductors are widely used as transparent electrodes in flat liquid crystal displays, touch panels, electroluminescent devices, and thin film photovoltaic cells; as antistatic layers; and as electromagnetic wave shielding layers.

Currently, vacuum deposited metal oxides, such as indium tin oxide (ITO), are industry standard materials for providing optical transparency and electrical conductivity to dielectric surfaces such as glass and polymer films. However, metal oxide films are fragile and susceptible to damage during bending or other physical stresses. It also requires high deposition temperatures and/or high annealing temperatures to achieve high levels of conductivity. In addition, vacuum deposition processes do not contribute to the formation of patterns and circuits. This often results in a costly patterning process (such as photolithography). In addition, metal oxide films tend to be difficult to properly adhere to certain substrates that are susceptible to moisture absorption, such as plastics and organic substrates (e.g., polycarbonate). Therefore, coating a metal oxide film on such flexible substrates is severely limited.

In recent years, it has tended to be embedded in a substrate in a flat panel display (the substrate is insulated or A composite of interconnected metal nanostructures (eg, silver nanowires) in conductive) replaces the current industry standard transparent conductive ITO film. Generally, a transparent conductive film is formed by first coating a coating solution including a metal nanowire, optionally a binder, and a volatile liquid carrier on a substrate. The binder, optionally selected, provides a matrix after removal of the volatile components of the ink composition. Regardless of the presence of the binder, the outer coating can be further applied after depositing the nanostructure. The outer coating typically comprises one or more polymeric or resinous materials. The sheet resistance of the obtained transparent conductive film can be comparable to or superior to the sheet resistance of the ITO film.

Coating techniques based on nanostructures are particularly useful for creating robust electronic components on large area flexible substrates. See U.S. Patent Nos. 8,049,333, 8,094,247, 8,018,568, 8, 174, 667, and 8, 018, 563, the disclosures of which are incorporated herein by reference. Solution-based forms for forming nanostructure-based films are also compatible with existing coating and lamination techniques. Thus, additional films of overcoat, undercoat, adhesive layer and/or protective layer can be integrated in a high throughput process for forming an optical stack comprising a nanostructure-based transparent conductor.

Other methods of forming a transparent conductor include the use of a fine patterned low sheet resistive grid or grid with a sputtered transparent conductor or conductive polymer to form a composite structure having the desired sheet resistance. In addition, a combination of a conductive nanostructure and a sputtered grid or grid can be used to achieve a relatively low resistance transparent conductor.

There remains a need in the art to provide a nanostructure-based transparent conductor having the desired electrical, optical, and mechanical properties that are maintained throughout the normal life of the transparent conductor.

Described herein is a thermally stable thin film transparent conductive layer that is thermally stable during an electrostatic discharge (ESD) event, specifically for high temperature gradients (eg, rapid temperature fluctuations over short periods of time).

One embodiment provides a transparent conductive film comprising a substrate; a conductive layer disposed on the substrate, the conductive layer having a plurality of interconnected conductive elements, the interconnects The conductive component is optionally embedded in the adhesive; and the outer coating, the outer coating covers the conductive layer, wherein at least one of the adhesive and the outer coating is a heat stable material.

In various embodiments, the binder can be a thermally stable material based on a thermally stable polymer such as polyimide or polybenzoxazole.

In other embodiments, the overcoat layer can be a thermally stable spin-on dielectric such as spin on glass (SOG).

In other embodiments, the overcoat layer can comprise a plurality of high heat capacity nanoparticles.

In various embodiments, the conductive layer can be a conductive nanostructure or a conductive mesh or a combination of mesh structures.

100‧‧‧Transparent conductive film

110‧‧‧Substrate

120‧‧‧film conductive layer

124‧‧‧ Conductive nanostructure

126‧‧‧Conductive Grid/Conductive Grid/Low Sheet Resistive Grid

130‧‧‧Interconnected conductive components

140‧‧‧Binder

150‧‧‧Ex overcoat

210‧‧‧Substrate

250‧‧‧Overcoat

260‧‧‧High heat capacity nano particles

300‧‧‧Transparent conductive film

310‧‧‧Substrate

312‧‧‧hard coating

314‧‧‧High heat capacity nano particles

350‧‧‧Overcoat

360‧‧‧High heat capacity nano particles

400‧‧‧Transparent conductive film

In the drawings, like reference numerals identify like elements. The dimensions and relative positions of the elements in the drawings are not necessarily to scale. For example, the shapes and angles of the various elements are not drawn to scale, and some of these elements are arbitrarily enlarged and positioned to enhance the intelligibility of the drawings. In addition, the particular shapes of the elements are not intended to convey any information about the actual shape of the particular elements, but are merely chosen for ease of identification in the drawings.

Figure 1 shows an embodiment of a transparent conductor having a thermally stable outer coating.

2A-2C show various configurations of conductive layers in accordance with embodiments of the present invention.

3 shows another embodiment of a transparent conductor having a thermally stable outer coating comprising a nanoparticle filler having a high heat capacity.

4 shows another embodiment of a transparent conductor having a thermally stable outer coating and a thermally stable primer.

Various embodiments are described herein with respect to transparent conductors based on mesh or nanostructures that are thermally stable during electrostatic discharge (ESD) events and less susceptible to structural damage that can be caused by transient heating.

During the processing or processing of a transparent conductor film, when sufficient electrostatic charge is accumulated and reaches An (ESD) event can occur when the electric field strength is sufficient to maintain the spark. In this event, the accumulated charge will move to a lower energy potential, such as a nearby conductive layer. As the electrostatic energy is discharged through the conductive layer, the conductive elements (eg, mesh and/or nanostructures) that carry the current in a thin film configuration can be instantaneously heated to well over 200 °C. It has been observed that film defects tend to occur after an ESD event, resulting in a decrease such as a decrease in conductivity or a loss in total conductivity.

SEM images of transparent conductive films show that damage to the organic phase (polymer binder or overcoat) may be associated with such degradation. The potential decay mechanism is that the heat from the conductive element causes vaporization and decomposition of the polymer binder and/or the outer coating, resulting in rapid accumulation of local pressure and subsequent degassing, similar to the process in which pressure accumulation is released via sharp gas phase diffusion. explosion. The "explosion" observed in the organic phase can be a major source of mechanical damage to the nanostructure or mesh.

Accordingly, one embodiment provides a transparent conductor having a thermally stable outer coating or adhesive that can withstand rapid temperature rise during the instant heating of the nanostructure. Therefore, a "thermally stable" material as used herein should be able to withstand high temperature gradients, i.e., large temperature changes (hundreds of degrees) over a very short period of time (about microseconds or seconds).

1 shows a transparent conductive film (100) comprising a substrate (110); a thin film conductive layer (120) disposed on a substrate (110), the conductive layer (120) having an embedded adhesive (140) a plurality of interconnected conductive elements (130); and an outer coating (150) covering the nanostructure conductive layer. At least one of the binder and the overcoat is a thermally stable material as defined herein.

In various embodiments, the conductive element (130) can be a plurality of randomly crossed conductive nanostructures. In other embodiments, the conductive elements are conductive grids or grids. Conductive grids or grids can intersect regularly or randomly. In other embodiments, the conductive element can be a composite film of a plurality of nanostructures that are electrically coupled into one or more conductive meshes or grids. Such a film is disclosed in U.S. Patent Application Serial No. 13/287,881, the disclosure of which is incorporated herein by reference.

2A-2B schematically illustrate various conductive elements forming the thin film conductive layer (120) of FIG.

In Figure 2A, the conductive element comprises a plurality of conductive nanostructures (124), in particular, metal nanowires. In a particularly preferred embodiment, the electrically conductive nanostructure is a silver nanowire. The conductive layer can be formed by coating a coating composition of a nanostructure on a substrate (e.g., 110 of Figure 1). The nanostructures are randomly distributed on the substrate, however a sufficient amount of nanostructures cross each other to form a conductive network that is capable of carrying current.

In FIG. 2B, the conductive layer (120) includes a conductive mesh or grid (126). A conductive grid (grid) is a network of low resistance paths or paths for current flow, distribution, and/or collection. The low sheet resistance grid 126 includes any type of electrically conductive structure having suitable electrical and physical properties, including metal, non-metal, or composite structures containing a combination of metallic and non-metallic structures.

In Figure 2C, the conductive layer (120) includes a combination of a plurality of nanostructures (124) and a grid (126).

Thermally stable materials have high heat capacity and/or can cause rapid heat dissipation to minimize thermal decomposition or outgassing. More specifically, the high thermal stability outer coating or adhesive is heated to above 200 ° C, or above 300 ° C, or above 400 ° C for a limited duration (such as lasting at least 10 seconds, or at least 30 seconds, or at least 60 The structural integrity can be maintained in seconds, or at least 2 minutes, or at least 4 minutes), or up to 1000 ° C for about microseconds (eg, at least 10 microseconds, or at least 100 microseconds). Structural integrity may include physical integrity (eg, no disintegration) and/or chemical integrity (eg, no decomposition), but the thermally stable material is capable of withstanding certain structural deformations or partial disintegration. For example, it can be melted (at least temporarily melted) as long as it is capable of absorbing or dissipating heat from the conductive material. In various embodiments, the thermally stable material should be capable of directing heat away from the electrically conductive material upon heating to above 400 ° C for at least 10 seconds, or at least 30 seconds, or at least 1 minute, or at least 4 minutes.

In various embodiments, the thermally stable material can be a spin-on dielectric material that can be An organic matter (such as cerium oxide), a polymer or a mixture thereof.

The thermally stable inorganic material that can be spin coated or coated includes materials comprising a siloxane (-Si-O-), a decazane (-NH-Si-) or a lanthanum carbide (-Si-C-) moiety, Zhongtong is called spin-on glass (SOG). SOG is commonly used as a gap fill and planarization dielectric layer in semiconductor processing.

SOG is typically deposited on a substrate by a sol-gel process and is thus compatible with solution-based methods of forming the transparent conductive films described herein. More specifically, once a stable suspension (sol) of colloidal particles is deposited, it irreversibly transforms into a rigid or porous membrane. Generally, a sol-gel process produces a network of polymers having a chemical moiety such as -Si-O-, -Si-NH- or -Si-C, or a combination thereof, via a hydrolysis-condensation reaction.

Organic polymers having high thermal stability tend to be crystalline, having an aromatic ring (including an aromatic ring fused to a non-aromatic ring) and one or more types of heteroatoms (such as nitrogen or oxygen). Exemplary polymers of high thermal stability include, but are not limited to, polybenzimine having an aromatic moiety, polybenzoxazole, and the like.

Another embodiment provides a transparent conductor having a coating having a high heat capacity and thermal conductivity such that heat released by the nanostructure or mesh can be rapidly absorbed or removed to minimize temperature increase in the organic phase.

More specifically, the overcoat layer may be a polymer layer or a resin layer which is largely filled with inorganic nanoparticles. 3 shows a transparent conductive film (300) comprising a substrate (210); a conductive layer (120) disposed on the substrate (210), the conductive layer (120) having a plurality of interconnected conductive elements (130) The interconnecting conductive elements are optionally embedded in a matrix or adhesive (140); and an outer coating (250) that covers the nanostructured conductive layer. The outer coating (250) comprises a plurality of high heat capacity nanoparticles (260).

The conductive layer (120) can be configured in any of Figures 2A, 2B, and 2C.

Due to the presence of high heat capacity nanoparticles, the highly filled outer coating tends to have a higher heat capacity than the outer filled outer coating. Therefore, the highly filled outer coating is much less likely to cause total outgassing by thermal decomposition than the final filled outer coating, and/or by heat and pressure. The total mechanical deformation caused by force is much less.

The high heat capacity nanoparticle is an inorganic particle having at least one dimension of less than 1 micron. The thermally conductive nanoparticles can be substantially spherical or elongated, such as in the shape of a nanowire or a nanotube. Nanoparticles of metal or metal oxide materials such as oxides of titanium, zinc, zirconium, aluminum and niobium are suitable thermal conductors. Certain non-metallic nanoparticles (such as carbon nanotubes and cerium oxide particles) can also be used.

The outer coating should be filled with thermally conductive nanoparticles at a loading that imparts a satisfactory heat capacity. The nanoparticles may or may not be in physical contact with each other. For a particular application, the amount of load can be determined empirically. Other factors (such as turbidity and light transmittance) can be varied by the amount and type of filled nanoparticle, and consideration should be given to balancing any conflicting needs. In various embodiments, the overcoat layer can be filled with at least 10% or at least 20%, or at least 30%, or at least 40% (v/v) of high heat capacity nanoparticle. The spin-on dielectric topcoat layer can comprise up to about 90% of nanoparticle.

The high heat capacity nanoparticle can be formulated into a coating solution with a predetermined loading amount and a polymer or a resin, and coated on a mesh or a nanostructure conductive layer. The overcoat layer may comprise a polymer such as, but not limited to, a polyacrylic acid (such as a polymethacrylate (eg, poly(methyl methacrylate)), a polyacrylate, and a polyacrylonitrile) , polyvinyl alcohol, polyester (such as polyethylene terephthalate (PET), polyphthalate and polycarbonate), highly aromatic polymers (such as phenolic resin or cresol-formaldehyde ( Novolacs ^® ), polystyrene, polyvinyltoluene, polyvinyl xylene, polyimide, polyamine, polyamidimide, polyether phthalimide, polysulfide, polyfluorene, polyphenylene And polyphenylene ether), polyurethane (PU), epoxy resin, polyolefin (such as polypropylene, polymethylpentene and cyclic olefin), acrylonitrile-butadiene-styrene copolymer ( ABS), cellulose systems, polyfluorene and other cerium-containing polymers (such as polysulfonium oxide and polydecane), polyvinyl chloride (PVC), polyacetate, polynorbornene, synthetic rubber (eg EPR, SBR, EPDM), fluoropolymers (such as polyvinylidene fluoride, polytetrafluoroethylene (TFE) or polyhexafluoropropylene), copolymers of fluoroolefins and hydrocarbon olefins (eg Lumi Flon ^® ) and amorphous fluorocarbon polymers or copolymers (eg CYTOP ^{® from} Asahi Glass Co. or Teflon ^® AF from Du Pont).

Another embodiment provides a transparent conductor having a nano-particle-filled hard coat under the mesh or nanostructure conductive layer in addition to or in addition to the nanoparticle-filled coating. Floor. The hard coat layer can further improve thermal stability by acting as a heat sink via higher heat capacity and thermal conductivity. 4 thus shows a transparent conductive film (400) comprising a substrate (310); a hard coat layer (312) covering the substrate (310) and comprising a second plurality of high heat capacity nanoparticles (314) a conductive layer (120) disposed on the hard coat layer (312), the conductive layer (120) having a plurality of interconnected conductive elements (130), the interconnected conductive elements being optionally embedded in the matrix or adhesive (140); and an outer coating (350), the outer coating covers the conductive layer, and the outer coating (350) further comprises a first plurality of high heat capacity nano particles (360).

The various components of the transparent conductive film are described in further detail below.

Conductive nanostructure

As used herein, "conductive nanostructure" generally refers to an electrically conductive nano-sized structure having at least one dimension (i.e., width or diameter) of less than 500 nm; more typically less than 100 nm or 50 nm. In various embodiments, the nanostructures have a width or diameter in the range of 10 to 40 nm, 20 to 40 nm, 5 to 20 nm, 10 to 30 nm, 40 to 60 nm, 50 to 70 nm.

One way to define the geometry of a given nanostructure is by its "aspect ratio", which is the ratio of the length to the width (or diameter) of the nanostructure. In a preferred embodiment, the shape of the nanostructure has an anisotropy (i.e., aspect ratio ≠1). Anisotropic nanostructures typically have a longitudinal axis along their length. Exemplary anisotropic nanostructures include nanowires (solid nanostructures having an aspect ratio of at least 10 and more typically at least 50), nanorods (solid nanostructures having an aspect ratio of less than 10), and nanotubes ( Hollow nanostructure).

The length of the longitudinal anisotropic nanostructure (e.g., nanowire) exceeds 500 nm, or exceeds 1 μm, or exceeds 10 μm. In various embodiments, the length of the nanostructure is between 5 and 30 μm Within the range, or in the range of 15 to 50 μm, 25 to 75 μm, 30 to 60 μm, 40 to 80 μm, or 50 to 100 μm.

Conductive nanostructures are typically metallic materials, including elemental metals (eg, transition metals) or metal compounds (eg, metal oxides). The metal material may also be a bimetallic material or a metal alloy containing two or more types of metals. Suitable metals include, but are not limited to, silver, gold, copper, nickel, gold plated silver, platinum, and palladium. It should be noted that although the present invention primarily describes nanowires (e.g., silver nanowires), any nanostructure within the above definitions may equally be employed.

Typically, the conductive nanostructures are metal nanowires having an aspect ratio in the range of 10 to 100,000. A larger aspect ratio may be advantageous to obtain a transparent conductor layer because it may enable the formation of a more efficient conductive mesh structure while allowing for lower bus density for high transparency. In other words, when a high aspect ratio conductive nanowire is used, the density of the nanowires that achieve the conductive network structure can be low enough to make the conductive network substantially transparent.

Metal nanowires can be prepared by methods known in the art. In particular, silver nanowires can be synthesized by solution phase reduction of a silver salt (e.g., silver nitrate) in the presence of a polyol (e.g., ethylene glycol) and poly(vinylpyrrolidone). Large-scale production of silver nanowires of uniform size can be made in accordance with the disclosure of the present application by the U.S. Patent Application Publication Nos. 2008/0210052, 2011/0024159, 2011/0045272 and 2011/ The process described in 0048170 is prepared and purified.

Nanostructured conductive layer

The nanostructure conductive layer is a conductive mesh structure interconnecting a conductive nanostructure (e.g., a metal nanowire) that provides a conductive medium for the transparent conductor. Since conductivity is achieved by charge infiltration from one metal nanostructure to another metal nanostructure, sufficient metal nanowires must be present in the conductive network to achieve an electrical permeation threshold and become conductive. of. The surface conductivity of the nanostructured conductive layer is inversely proportional to its surface resistivity, which is sometimes referred to as sheet resistance, which can be measured by methods known in the art. As used herein, "electrically conductive" or simply "conductive" corresponds to no more than 10 ⁴ Ω/□, or more typically no more than 1,000 Ω/□, or more typically no more than 500 Ω/□. Or, more typically, does not exceed a surface resistivity of 200 Ω/□. The surface resistivity depends on the following factors of the interconnected conductive nanostructure, such as aspect ratio, degree of alignment, degree of coalescence, and resistivity.

In certain embodiments, the conductive nanostructures can form a conductive network on the substrate without a binder. In other embodiments, a binder may be present to promote adhesion of the nanostructure to the substrate. Suitable adhesives include optically clear polymers including, but not limited to, polyacrylic acids (such as polymethacrylates (eg, poly(methyl methacrylate)), polyacrylates, and Polyacrylonitrile), polyvinyl alcohol, polyester (such as polyethylene terephthalate (PET), polyphthalate and polycarbonate), highly aromatic polymers (such as phenolic resin or nail) Phenol-formaldehyde (Novolacs ^® ), polystyrene, polyvinyl toluene, polyvinyl xylene, polyimine, polyamine, polyamidimide, polyether phthalimide, polysulfide, poly Bismuth, polyphenylene and polyphenylene ether), polyurethanes (PU), epoxy resins, polyolefins (eg polypropylene, polymethylpentene and cyclic olefins), acrylonitrile-butadiene-benzene Ethylene copolymer (ABS), cellulose compounds, polyfluorene oxide and other cerium-containing polymers (such as polysulfonium oxide and polydecane), polyvinyl chloride (PVC), polyacetate, polynorbornene, Synthetic rubber (eg EPR, SBR, EPDM), and fluoropolymers (eg polyvinylidene fluoride, polytetrafluoroethylene (TFE) or polyhexafluoropropylene), fluoroolefins The hydrocarbon olefin copolymer (e.g., Lumiflon ^®), and amorphous fluorocarbon polymers or copolymers (e.g., CYTOP ^® Asahi Glass Co., or of the Du Pont Teflon ^® AF). Other suitable binders include carboxymethyl cellulose (CMC), 2-hydroxyethyl cellulose (HEC), hydroxypropyl methyl cellulose (HPMC), methyl cellulose (MC), polyvinyl alcohol (PVA). ), tripropylene glycol (TPG) and xanthan gum (XG).

"Substrate" means a non-conductive material coated or laminated with a metallic nanostructure. The substrate can be rigid or flexible. The substrate can be clear or opaque. Suitable for rigid substrates These include, for example, glass, polycarbonate, acrylics, and the like. Suitable flexible substrates include, but are not limited to, polyesters (eg, polyethylene terephthalate (PET), polyphthalate and polycarbonate), polyolefins (eg, linear, branched) And cyclic polyolefin), polyethylene (such as polyvinyl chloride, polyvinylidene chloride, polyvinyl acetal, polystyrene, polyacrylate and the like), cellulose ester matrix (such as cellulose triacetate, Cellulose acetate), polyfluorene (such as polyether oxime), polyimine, polyfluorene, and other conventional polymer films. Other examples of suitable substrates can be found, for example, in U.S. Patent No. 6,975,067.

Generally, the optical transparency or clarity of a transparent conductor (i.e., a conductive mesh structure on a non-conductive substrate) can be quantitatively determined by parameters including light transmittance and turbidity. "Light transmission/light transmissivity" refers to the percentage of incident light transmitted through the medium. In various embodiments, the conductive layer has a light transmission of at least 80% and can be as high as 98%. A performance enhancing layer, such as an adhesive layer, an anti-reflective layer, or an anti-glare layer, can further contribute to reducing the total light transmission of the transparent conductor. In various embodiments, the transparent conductor may have a light transmission (T%) of at least 50%, at least 60%, at least 70%, or at least 80%, and may be as high as at least 91% to 92%, or at least 95%.

Turbidity (H%) is a measure of light scattering. It refers to the percentage of light that is separated from incident light and scattered during transmission. Unlike light transmission, which is essentially a property of the medium, turbidity is often a production concern and is typically caused by surface roughness and embedded particles or compositional heterogeneity in the medium. Generally, the turbidity of the conductive film can be significantly affected by the diameter of the nanostructure. Larger diameter nanostructures (eg, thicker nanowires) are often associated with higher turbidity. In various embodiments, the haze of the transparent conductor does not exceed 10%, does not exceed 8% or does not exceed 5%, and can be as low as no more than 2%, no more than 1% or no more than 0.5%, or no more than 0.25% .

Coating composition

The patterned transparent conductor of the present invention is prepared by coating a coating composition containing a nanostructure on a non-conductive substrate. To form a coating composition, usually a metal nanowire Dispersed in a volatile liquid to promote the coating process. It should be understood that any non-corrosive volatile liquid in which the metal nanowires can form a stable dispersion can be used as used herein. Preferably, the metal nanowire is dispersed in water, an alcohol, a ketone, an ether, a hydrocarbon or an aromatic solvent (benzene, toluene, xylene, etc.). More preferably, the liquid is volatile and has a boiling point of no more than 200 ° C, no more than 150 ° C or no more than 100 ° C.

In addition, the metal nanowire dispersion may contain additives and binders to control viscosity, corrosion, adhesion, and nanowire dispersion. Examples of suitable additives and binders include, but are not limited to, carboxymethyl cellulose (CMC), 2-hydroxyethyl cellulose (HEC), hydroxypropyl methyl cellulose (HPMC), methyl cellulose. (MC), polyvinyl alcohol (PVA), tripropylene glycol (TPG) and Sanxian gum (XG), and surfactants (such as ethoxylates, alkoxylates, ethylene oxide and propylene oxide) and Its copolymers, sulfonates, sulfates, disulfonates, sulfosuccinates, phosphates, and fluorosurfactants (such as Zonyl ^{® from} DuPont).

In one example, a nanowire dispersion (or "ink") comprising by weight from 0.0025 to 0.1% surfactant (for example Zonyl ^® FSO-100, preferably in the range from 0.0025 to 0.05%), 0.02% To 4% viscosity modifier (for example, 0.02% to 0.5% for HPMC), 94.5% to 99.0% solvent, and 0.05% to 1.4% metal nanowire. Representative examples of suitable surfactants include ^{Zonyl ® FSN, Zonyl ® FSO,} Zonyl ® FSH, Triton (x100, x114, x45), Dynol (604,607), n-dodecyl maltoside and bD- Novek. Examples of suitable viscosity modifiers include hydroxypropyl methylcellulose (HPMC), methylcellulose, trisin, polyvinyl alcohol, carboxymethylcellulose, and hydroxyethylcellulose. Examples of suitable solvents include water and isopropanol.

The concentration of the nanowires in the dispersion affects or determines the parameters of the nanowire network layer, such as thickness, electrical conductivity (including surface conductivity), optical clarity, and mechanical properties. The percentage of solvent can be adjusted to provide the desired concentration of nanowires in the dispersion. However, in the preferred embodiment, the relative ratios of the other ingredients may remain the same. In particular, the ratio of surfactant to viscosity modifier is preferably in the range of from about 80 to about 0.01; viscosity modifiers and The ratio of the metal nanowires is preferably in the range of from about 5 to about 0.000625; and the ratio of the metal nanowire to the surfactant is preferably in the range of from about 560 to about 5. The ratio of the components of the dispersion can be adjusted depending on the substrate used and the coating method. The preferred viscosity range for the nanowire dispersion is from about 1 to 100 cP.

After coating, the volatile liquid is removed by evaporation. Evaporation can be accelerated by heating (e.g., baking). The resulting nanowire network layer may require post treatment to render it electrically conductive. Thereafter the treatment can be a process step involving exposure to heat, plasma, corona discharge, UV-ozone or pressure as described below.

Examples of suitable coating compositions are described in U.S. Published Application No. 2007/0074316, No. 2009/0283304, No. 2009/0223703, and No. 2012/0104374, the name of the assignee of the present disclosure.

The coating composition is coated on a substrate by, for example, sheet coating, web-coating, printing, and lamination to provide a transparent conductor. Other information for the manufacture of a transparent conductor from a conductive nanostructure is disclosed in, for example, U.S. Published Application No. 2008/0143906 and No. 2007/0074316, the disclosure of which is incorporated herein by reference.

Conductive grid or grid

A low sheet resistance grid (e.g., 126 of Figures 2B and 2C) provides a network of low resistance paths or paths for current flow, distribution, and/or collection. The low sheet resistance grid 126 includes a conductive structure having any type of suitable electrical and physical properties, including metal structures, non-metal structures, or composite structures containing a combination of metal and non-metal structures. Examples of low sheet resistance grids 126 include, but are not limited to, fine metal grids (eg, copper grids, silver grids, aluminum grids, steel grids, etc.) that are patterned and deposited, for example, by sputtering or evaporation. Preferably, for example, a screen printing metal paste (for example, an Ag paste), an insertable fine metal wire or a printable solution containing one or more residual low resistance components.

The physical dimensions and/or configuration of the low sheet resistance grid 126 is based, in whole or in part, on meeting any specified electrical requirements (eg, sheet resistance) and physical requirements (eg, surface roughness and/or Or light transmittance). The size and routing of the conductors forming the low sheet resistance grid 126 form a grid pattern for depositing or otherwise forming at least a portion of the low sheet resistance grid 126 on the substrate. In some embodiments, the width of the elements forming the low sheet resistance grid 126 can range from about 1 micron to about 300 microns. In some embodiments, the height of the elements forming the low sheet resistance grid can range from about 100 nm to about 100 microns. The open distance between the elements forming the low sheet resistance grid can range from about 100 microns to about 10 mm.

The deposition of the low sheet resistance grid 126 can be accomplished using pre-patterning, post-patterning, or any combination thereof. Examples of pre-patterned, printed low sheet resistance grids include, but are not limited to, printed silver paste grids, printed copper paste grids, microparticle or nanoparticle paste grids, or similar conductive paste grids grid. An exemplary post-patterned low sheet resistance grid 126 is provided by photolithographic development using a pre-coated conductive film to produce a low sheet resistance grid 126. Other exemplary post-patterned low sheet resistance grids 126 include, but are not limited to, total deposition via printing, evaporation, sputtering, electroless plating or electrolytic plating, or solution processing, followed by photolithography, Screen printing resists, screen printing etchants, standard etching, laser etching, and adhesives are used to remove the stamps for patterning.

The low sheet resistance grid can have any two or three dimensional geometry, shape or configuration required to achieve the desired sheet resistance while maintaining acceptable optical properties. Although a larger grid density (i.e., a larger low resistance path across the cross-sectional area) can reduce the overall sheet resistance of the transparent conductor, the high grid density can increase the opacity of the transparent conductor to an unacceptable extent. Thus, the pattern selection and physical properties of the low sheet resistance grid 126 can sometimes be based, at least in part, on the trade-off that minimizes the sheet resistance of the transparent conductor while not increasing the opacity of the transparent conductor to an unacceptable level.

The low sheet resistance grid 126 can have any fixed, geometric or random pattern capable of providing an acceptable sheet resistance. For example, the low sheet resistance grid 126 pattern can include a geometric arrangement of regular or irregular widths, such as vertical lines, angled lines (eg, forming a "diamond" pattern), and parallel lines. Other patterns can use curved or curved conductors to achieve A complex pattern of one or a non-uniform sheet resistance, such as a complex pattern in which a transparent conductor is intended for three-dimensional applications. Where appropriate, for example, in some OLED series interconnected cells and in forming photovoltaic modules, two or more patterns may be used to form the low sheet resistance grid 126, for example using a larger pattern (such as A hexagonal or rectangular) grid of bounded parallel lines. In another embodiment, the low sheet resistance grid 126 can be a comb structure that connects the tandem interconnected thin film photovoltaic strips.

Instance Example 1

Standard preparation of coating compositions for conductive nanostructures

A typical coating composition for depositing a metal nanowire comprises 0.0025% to 0.1% by weight of a surfactant (e.g., for a fluorosurfactant, preferably from 0.0025% to 0.05%), 0.02% to 4% viscosity. Modifiers (for example, hydroxypropyl methylcellulose (HPMC), preferably in the range of 0.02% to 0.5%), 94.5% to 99.0% solvent, and 0.05% to 1.4% metal nanowires.

The coating composition can be prepared based on the desired nanowire concentration, which is an index of the loading density of the final conductive film formed on the substrate.

The coating composition can be deposited on a substrate according to, for example, the method described in U.S. Patent No. 8,049,333 and U.S. Patent Application Serial No. 2011/0174190.

As will be appreciated by those skilled in the art, other deposition techniques can be employed, such as sedimentation flow metered by narrow channels, mold flow, bevel flow, slot coating, gravure coating, microgravure coating, droplet coating, dip coating. Cloth, slot die coating and similar techniques. Printing techniques can also be used to print the ink composition directly onto the substrate in the presence or absence of a pattern. For example, inkjet, flexographic, and screen printing can be employed. It is further understood that the viscosity and shear behavior of the fluid and the interaction between the nanowires can affect the distribution and interconnectivity of the deposited nanowires.

A sample conductive nanostructure dispersion was prepared, which contained the silver neon as manufactured in Example 1. Rice noodles, surfactants (such as Triton) and viscosity modifiers (such as low molecular weight HPMC) and water. The final dispersion included about 0.4% silver and 0.4% HPMC (by weight), that is, a weight ratio of 1:1.

Example 2

Silver nanowire layer coated with spin-on glass (SOG)

1. Preparation of silver nanowire film with or without Ar plasma treatment

A coating solution of silver nanowire (AgNW) was prepared according to the general method described in Example 1. HPMC is available from Dow Chemicals (Methocel ^® 311 and K100).

The coating solution was spin coated onto 8 glass samples (slides). The AgNW coated glass samples were then dried at 50 °C for 90 seconds and baked at 140 °C for 90 seconds. The AgNW film samples were divided into two groups of four samples each. The initial sheet resistance of the first set was measured. The four membranes of the second set were subjected to an argon (Ar) plasma treatment to remove the binder (eg, HPMC). See Table 1. The sheet resistance was measured after Ar plasma treatment.

2. Coating spin-on glass on AgNW film

Spin-on glass (SOG) is available from Silec Co, product number SG230.

Two sets of samples (1-8) were coated with SOG using the following procedure: (1) SG230 diluted with isopropyl alcohol (IPA) (1:1 by volume or 1:3 by volume), (2) continued at 1000 rpm The resulting SOG solution was spin coated onto the AgNW film for 30 seconds and (3) the sample was baked at 140 ° C for 5 minutes.

Table 2 shows the initial sheet resistance (SR) / light transmittance (T) and turbidity of the AgNW film. (H), and contact resistance of the SOG coated AgNW film.

Samples with higher dilutions showed better contact resistance, indicating a thinner SOG film. A slight increase in sheet resistance after SOG deposition was observed, but the overall integrity of the AgNW was preserved. In addition, due to the presence of SOG in the optical stack, the transmittance is slightly increased and the turbidity is slightly lowered.

Example 3

Thermal stability of SOG coated film

The sample of Example 2 was exposed to heat treatment to investigate the thermal stability of the AgNW film. A set of four samples was heated in a blast furnace at 350 ° C for one minute (t = 1), and another set of four samples was heated to 400 ° C for one minute (t = 1). Sheet resistance (SR), light transmittance (T), and haze (H) after heat treatment are shown in Table 3.

As shown, the sheet resistance of samples made with ink from Methocel ^® K100 increased more sharply than the sheet resistance of samples made with Methocel ^® 311. Nonetheless, in the absence of a SOG overcoat, the nanowires disintegrate at about 180 °C. Thus, the ability of SOG coated nanowire films to withstand 400 °C over a long period of time indicates that SOG provides thermal protection and prevents nanowire collapse.

Sustained thermal stability was observed in these samples when samples of Methocel ^® 311 (sample Nos. 1 and 3) were further heated at 400 ° C for 4 minutes (t = 4) and well over 4 minutes. See Table 4.

A decrease in turbidity was observed in samples using Methocel ^® K100 (sample numbers 6 and 8) indicating that the nanowires were at least partially disintegrated. Subsequent optical microdata confirmed the disintegration and disappearance of the silver nanowire structure in these samples.

The various embodiments described above can be combined to provide additional embodiments. All U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications, and non-patent publications mentioned in the specification and/or application form are referred to in full by reference. Incorporated herein. The embodiments may be modified as necessary to provide further embodiments in the concept of various patents, applications, and publications.

These and other changes can be made to the embodiments in light of the above detailed description. In general, the terms used in the following claims should not be construed as limiting the scope of the claims to the specific embodiments disclosed in the specification and claims. The full range of equivalents of the scope. corresponding The scope of patent application is not limited by the disclosure.

100‧‧‧Transparent conductive film

110‧‧‧Substrate

120‧‧‧film conductive layer

130‧‧‧Interconnected conductive components

140‧‧‧Binder

150‧‧‧Ex overcoat

Claims (17)

A transparent conductive film comprising: a substrate; a conductive layer disposed on the substrate, the conductive layer having a plurality of interconnected conductive elements, the interconnected conductive elements being embedded in the adhesive as appropriate; and a coating, the outer coating covering the conductive layer, wherein at least one of the adhesive and the outer coating is a heat stable material. The transparent conductive film of claim 1, wherein the binder is polyimine or polybenzoxazole. The transparent conductive film according to any one of claims 1 to 2, wherein the outer coating layer is polyimide or polybenzoxazole. The transparent conductive film according to any one of claims 1 to 3, wherein the outer coating layer is a spin-on dielectric layer. The transparent conductive film of claim 4, wherein the spin-on dielectric layer comprises a network of polymers having a portion of -Si-O-, -Si-NH-, -Si-C-, or a combination thereof. The transparent conductive film of claim 4, wherein the outer coating is a spin-on glass. The transparent conductive film of any one of claims 1 to 6, wherein the heat stable material is capable of maintaining its structural integrity when heated to above 400 ° C for at least 1 minute. The transparent conductive film of any one of claims 1 to 6, wherein the heat stable material is capable of maintaining its structural integrity when heated up to 1000 ° C for at least 100 microseconds. The transparent conductive film of any one of claims 1 to 3, wherein the outer coating layer comprises a first plurality of high heat capacity nano particles. The transparent conductive film of claim 9, further comprising a hard coat layer interposed between the substrate and the conductive layer, the hard coat layer having a second plurality of high heat capacity nano particles. The transparent conductive film according to any one of claims 9 to 10, wherein the high heat capacity nanoparticles are oxides of cerium, titanium, zinc, zirconium, aluminum and cerium. The transparent conductive film of any one of claims 9 to 10, wherein the high heat capacity nanoparticles are carbon nanotubes. The transparent conductive film of any one of claims 1 to 12, wherein the conductive elements are a plurality of conductive nanostructures. The transparent conductive film of any one of claims 1 to 12, wherein the conductive elements form a conductive mesh. The transparent conductive film of any one of claims 1 to 12, wherein the conductive layer comprises a plurality of conductive nanostructures electrically coupled to the conductive mesh. The transparent conductive film of claim 13 or 15, wherein the conductive nanostructures are silver nanowires. A transparent conductive film according to claim 14 or 15, wherein the conductive mesh is formed of a metal paste or a conductive wire.